Phys A L17-18 - Physical Anthropology Lecture 17-18(Chapter...

Physical Anthropology: Lecture 17-18 (Chapter 10) I. Geological, Climate and Biological Conditions A. To understand the evolution of our species, it is important to understand the geological, climatic and biological conditions under which these changes occurred! B. The positions of the continents have changed relative to each other and to the poles C. Continental drift is the movement of continents 1. 200 mya—continents joined together, single huge landmass = Pangae 2. 135 mya Pangae began to break apart into separate pieces, Northern half = Laurasia [North America, Eurasia (minus India)], Southern half = Gondwanaland 3. 65 mya Gondwanaland had broken up into several smaller pieces Africa and India separate, India heads North, eventually Gondwanaland separated into South America, Antarctica and Australia 4. South America did not drift north to join North America until ~ 5mya D. Continental drift is important because: 1. Oceans act as barriers creating isolation for allopatric speciation (evolution of species) 2. One of the engines of climatic change. The climate has changed dramatically over the last 65 million years. First becoming warmer and less variable, then cooling and finally fluctuating widely in temperature E. Climatic Reconstructions 1. Large continents tend to have severe weather 2. When continents restrict circulation water from tropics to the poles, world climates seem to become cooler II. Fossil Dating A. There are several radiometric methods for dating the age of fossils B. Radiometric methods : Use the radioactive decay of unstable elements to more stable ones to age the earth 1. Examples: Potassium – Argon, C14, thermo-luminescence, electron spin, uranium series C. Absolute radiometric dating is supplemented by relative dating methods based

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